Study on quality attributes and drying kinetics of instant parboiled rice fortified with turmeric using hot air and microwave-assisted hot air drying

Abstract

This study investigated the quality and drying kinetics of instant parboiled rice fortified with turmeric (IPRFT) by using hot air (HA) and microwave-assisted hot air (MWHA) drying. The cooked long grain parboiled rice (LGPR) fortified with turmeric was dried with HA at temperatures of 65, 80, 95, and 110 °C. The microwave power density of 0.588 Wg⁻¹ was incorporated for drying with MWHA. Drying was performed until the dried IPRFT reached 16% (d.b.) of moisture content. The quality of the dried IPRFT was evaluated in terms of color, total phenolics content (TPC), total antioxidant capacity (TAC), rehydration ratio, volume expansion ratio, texture and microstructure. The results showed that the incorporation of microwave power with HA drying helped to reduce the drying time by 50% compared to conventional HA drying. A prediction of the moisture ratio by using the Page model provided the best R² and RMSE in drying kinetics. The drying conditions had small effects on the color, TPC, TAC, and microstructure of the dried IPFRT. The rehydration ratio, volume expansion ratio and texture of the rehydrated IPFRT showed minimal variations from changes in the drying conditions. The TPC and TAC of the dried IPRFT clearly increased compared to the TPC and TAC of the initial LGPR.

Keywords:

• Antioxidant
• drying
• drying kinetics
• functional foods
• instant rice
• parboiled rice
• turmeric

Acknowledgments

The authors also thank to Prof. Dr. Vijaya Raghavan and related staffs at Department of Bioresource Engineering, Faculty of Agricultural and Environmental Sciences, McGill University (Macdonald Campus), Canada that helped to support materials and equipment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors express their sincere appreciation to the Thailand Research Fund (TRF) under the Royal Golden Jubilee Ph.D. Program (Grant number: PHD/0209/2551), King Mongkut’s University of Technology Thonburi (KMUTT) and TRF Distinguished Research Professor Grant to Prof. Somchart Soponronnarit (Grant No. DPG 5980004) for their financial support.